Continuously adjustable controls for oil burners

ABSTRACT

Continuously adjustable oil burner controls which include an electromagnetic metering valve in the fuel oil return line, the metering valve determining the supply of fuel oil to the atomizer nozzle of the burner as a function of the coil current which determines the throttling effect of the metering valve and thus the pressure in the fuel oil supply line. The latter also controls the air intake of a combustion air blower.

United States Patent 1 [11] 3,840,323

Eckerle et al. Oct. 8, 1974 [54] CONTINUOUSLY ADJUSTABLE CONTROLS3,547,093 12/1970 Sherman 431/89 X FOR 01 BURNERS 3,592,574 7/1971Ettlingen 431/90 3,684,238 8/1972 Michellone 251/141 X [75] Inventors:Otto Eckerle, Benzstr. 6; Robert Hugo Jung, both of Malsch, GermanyPrimary Examiner-Edward G. Favors 73 Assignee: said Eckerle, by saidJung Almmey Agen" 661g [22] Filed: May 14, 1973 [21] App]. No.: 359,728[57] ABSTRACT Continuously adjustable oil burner controls which in-'[30] Forelgn Apphcatmn Pnomy Data clude an electromagnetic meteringvalve in the fuel oil Oct. 4, 1972 Germany 2248674 return line themetering valve determining the Supply of fuel oil to the atomizer nozzleof the burner as a 2:51 hits. (51. "his 131mg function of the Coilcurrent which determines the d 5 2 throttling effect of the meteringvalve and thus the 1 0 pressure in the fuel oil supply line. The latteralso con- 5 References Cited trols the air intake of a combustion airblower.

UNITED STATES PATENTS 12 Claims, 3 Drawing Figures 2,979,124 4/1961 Kirk431/90 CONTINUOUSLY ADJUSTABLE CONTROLS FOR OIL BURNERS BACKGROUND OFTHE INVENTION 1. Field of the Invention The present invention relates tooil burner controls, and in particular to automatically adjustable oilburner controls which are capable of varying the fuel and air supply tothe burner so as to adjust its heat output within a wide range, whilemaintaining an optimal combustion ratio of fuel and air.

2. Description of the Prior Art Attempts have been made in the past toprovide oil burner controls which incorporate means for adjusting thefuel and air supply to the burner, in order to vary its heat output. Onesuch prior art solution suggests a system where an electric motor drivesa control cam which engages a push rod controlling a spring-biasedthrottle valve whose setting determines the oil supply pressure andcombustion rate. The cam position thus determines, via the intermediatepush rod, the opening of the throttle valve, the latter setting theatomizing pressure and consequently the heat output. Although thissolution is a comparatively reliable one, it is complex and thereforevery expensive.

Another prior art solution suggests the arrangement of a pressurecontrol valve in the return line of a plunger shutoff valve, whereby theatomizing pressure is adjusted. This solution is relatively simple;however, it cannot be used in conjunction with automatic burner controlswhich use a thermastat, or a switching timer, or similar pre-settablecontrols.

SUMMARY OF THE INVENTION It is a primary objective of the presentinvention to suggest a simple, inexpensive system of continuouslyadjustable oil burner controls which is free of the above-mentionedshortcomings.

The present invention proposes to attain the above objective bysuggesting an oil burner control system which uses anelectromagnetically controlled metering valve, whereby an electromagnetdetermines the opening of the metering valve as a function of theelectric current being applied to it, the latter being convenientlyadjustable by means ofa potentiometer, for ex- Among the advantagesoffered by the present invention are its reliability of operation over awide range of adjustment settings and its simplicity of design andcorrespondingly low production costs.

BRIEF DESCRIPTION OF THE DRAWINGS Further special features andadvantages of the inven tion will become apparent from the descriptionfollowing below, when taken together with the accompanying drawingswhich illustrate, by way of example, several embodiments of theinvention, represented in the various figures as follows:

FIG. 1 shows a first embodiment of the invention in which a portion ofthe fuel pump and the metering valve are shown in cross section, thethrough-flow atomizer nozzle and the remainder of the oil burner systembeing shown schematically;

FIG. 2 shows a second embodiment of the invention, similarly representedas a partial cross section in combination with a schematicrepresentation of the oil burner system, the latter including abypass-type atomizer nozzle; and

FIG. 3 shows in an enlarged elevational cross section the metering valveof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first embodiment of theinvention, illustrated in FIG. 1, an electric motor 6 drives a fuel pump4 and a combustion air blower 8. A suction'line 3 connects the fuel oilpump 4 to a fuel oil reservoir 2 from which the latter'pumps fuel oilthrough the channels 39 and 37, and via a bore in the pole core 34, intothe return line 40, from where the fuel oil returns to the reservoir vialine 1. The blower wheel 8 simultaneously takes in air through an intakeAs which is determined by the movement of an air clappet 11 against theintake opening of the housing 12 of the combustion air blower. The

combustion air passes through air conduits 13 and 16 into the combustionchamber (not shown in the drawing).

As long as the electromagnetic coil 28 is not energized, a back pressurevalve, consisting of a ball 23, a spring 22 and a set screw 21, preventsthe recirculating fuel oil from passing through channel 24, via the Ithreaded bore 20, into the atomizer line 18 of the atomample. Thepotentiometer in turn may be part of a ther- I biased against the valveseat in response to the magnet coil current, so that the gap between thevalve seat and the armature forms a variable throttling passage whichdetermines the fuel oil supply pressure. This throttling passage iseither arranged in the fuel oil return line which is branched to thefuel oil supply line, between the oil pump and the atomizer nozzle, orit is arranged in the return line between the atomizer nozzle and theoil reservoir, in the case of a bypass-type atomizer nozzle.

izer nozzle 17.

A readjustment of a potentiometer 36 admits an electric current to coil28 so as to pull the armature 33 inside the electromagnet toward thevalve seat on the upper side of pole core 34, thereby reducing thethrottling gap between the armature and the valve seat. The force withwhich the armature 33 is urged against the valve seat of pole core 34 isa function of the current that flows through coil 28 and this forcedetermines the oil pressure which is required in the center bore of polecore 34, in order tokeep the metering valve open. The pressure buildupdue to the throttling pressure of the armature 33 against the valve seatof pole core 34 causes the ball 23 of the back pressure valve to openagainst the biasing spring 22 so that some of the fuel oil flows throughchannels 20 and 18 to the atomizer nozzle 17, the fuel oil pressure atthe nozzle being determined by the armature position of the meteringvalve.

The air clappet 11 which determines the air intake gap As with thehousing 12 of the combustion air blower is part of a hydraulic controlcylinder 9 in which the plunger is stationary while the cylinder itselfis axially movable in response to the pressure in the fuel oil supplychannel 39, thereby opening the air clappet 11 against a biasing spring10. The hydraulic cylinder 9 communicates with the supply channel 39 viaa control line l9, 15, 14. An increase in the oil supply pressure causedby the adjustment of control member 35 causes the hydraulic cylinder 9and the air clappet 11 to move against spring 10 so as to increase theair intake gap As, reducing the throttling effect of air clappet 11 onthe blower intake accordingly, so as to admit more air to the latter.Through appropriate coordination of the characteristics of the biasingspring 10, of the cylinder 9, and of the size of the air clappet 11 withthe atomizing characteristics of nozzle 17, it is thus possible toobtain automatically an optimal combustion mixture of fuel oil and airwithin a wide range of supply pressures as adjusted through controllever 35.

The electromagnetic metering valve thus constitutes an essential elementof the oil burner system. The coil 28 of the metering valve issurrounded in a known manner by an iron circuit which consists of a yokebracket 30 and a yoke plate 27. At the inside of coil 28 is arranged aguide sleeve 32 of magnetically nonpermeable material which serves as aguide for the axially movable armature 33 and which forms a hermeticseal in cooperation with a gasket 26, positioned against the pumphousing 25 on which the metering valve is mounted. The guide sleeve 32thus hermetically encloses the stationary pole core 34 and the movablearmature 33 which constitute the throttling elements of the meteringvalve.

The electromagnetic metering valve is preferably designed for operationwith d-c current, and it may be connected in a parallel circuit with theelectric motor 6, the d-c circuit being supplied by a rectifying bridgecircuit 38, for example.

In FIG. 2 is shown a second embodiment of the invention in whichv theatomizer nozzle 43 is of the bypass-type (with a return line to the fueloil reservoir). This embodiment requires in addition to the meteringvalve a plunger shutoff valve 55 which assures a constant supplypressure in the fuel oil supply line 45 leading to nozzle 43, themetering valve being arranged in the return portion of the flow circuit.This embodiment has the advantage of a still wider range of adjustmentswhich is possible through the use of the bypass-type atomizer nozzle 43.

Before combustion startup, and at the beginning of the operation of pump4, the plunger shutoff valve 55 keeps both the connection 48 to thenozzle line 45 and the connection 54 to the return line 1 closed, theshutoff valve position as shown in FIG. 2 indicating a positive closingoverlap a for connection 48 and a somewhat larger positive closingoverlap b for connection 54. As soon as the pressure against the plungerof the shutoff valve 55 reaches the predetermined operating value set bya biasing spring, the positive closing overlap a is eliminated so thatpressurized fuel oil flows through the channels 48, 47, 46, 45 into theatomizer nozzle 43. If the supply pressure from pump 4 increases stillfurther, the positive closing overlap b likewise disappears, therebyopening an overflow connection to the fuel oil reservoir 2 viaconnection 54 and return line 1.

As long as the electromagnetic metering valve is not supplied with anelectric current, a major portion of the fuel oil fed to the atomizernozzle 43 returns to the reservoir via the bypass line system 44, 49,50, 51, because only a minimal flow resistance is present in this lineportion. Thus, the amount of fuel oil being atomized by passing throughthe atomizer nozzle 43 itself is minimal and corresponds to the lowerend of the adjustment range of the nozzle. The air intake gap As of thecombustion air blower is accordingly narrow, the position of the airclappet 11 being determined by the pressure in the return line 44 whichis connected to the cylinder 9 of the air clappet 11 via a control line42. The response characteristics of the biasing spring 10, of the airclappet 11, and of the atomizer nozzle 43 are again coordinated so as toobtain an optimal mixing ratio of fuel oil and combustion air. Theadjustment of the flow rate through the atomizer nozzle 43 is againobtained by means of a control lever 35 which adjusts a potentiometer 36controlling the electric current flowing through coil 28 of theelectromagnetic metering valve. The latter is of the same type asdescribed previously. However, in this case the metering valve isarranged in the bypass-line portion 44, 49, 50, 52, 53, 1 through whichthe fuel oil returns to the reservoir 2. A movement of the armature ofthe metering valve thus increases the resistance in the bypass-line,thereby causing the quantity of oil being atomized in the atomizernozzle 43 to be similarly increased. The higher pressure in the bypassline 44 simultaneously causes the air clappet control cylinder 9 to moveagainst the spring 10 so as to admit more combustion air through theintake gap As. With appropriately coordinated response characteristicsas previously described, the oil burner system of the invention permitsa continuous adjustment of the rate of combustion within a wide rangeand under optimal combustion conditions.

The electromagnetic metering valve of the invention is illustrated inmore detail, and at an enlarged scale, in FIG. 3 of the drawing. As canbe seen from this illustration, the throttling elements of the valve areof the flatseat type, although they could likewise be of any othersuitable type. The flat-seat valve has the following advantages:

a. No precision-machined parts are needed, and the requirement of smalleffective areas for the armature and for the pole core is met;

b. In the fully energized condition of the electromagnet the armature 33is almost closed against the pole core 34 so as to provide an excellentflow path for the magnetic field, the advantage of this arrangementbeing that the magnetic energy is used optimally and that the operatingtemperature of the coil 28 is therefore kept low;

c. The valve seat is not very sensitive against the accumulation ofdeposits, the latter being continuously removed by the fuel oil flow,under the action of the armature against the valve seat;

d. The highest pumping pressure acting against the electromagneticmetering valve when the latter is closed, is only reached very shortlybefore the valve is completely closed, the required valve closing forcedetermined by the hydrostatic load on the armature being therefore onlyrequired in a position of the armature which is magnetically desirable,i.e. when the armature is as little as 0.5 to 1 mm from the pole core,in which position the force flow of the magnetic field is accordinglygreater, thereby conveniently providing the required higher holdingforce against the metering valve.

In order to reduce the pressure-affected area of the valve, the seat ofpole core 34 is provided with a circular relief groove 60 whichcommunicates with two lateral return flow grooves 61. This arrangementeliminates the pressure against the seat area outside the circularrelief groove 60.

It was found, however, that the fuel oil which passes through thecentral bore 59 of pole core 34 may lead to a pressurization of theupper end face of armature 33, as a result of being deflected from theinner wall of the guide sleeve 32, after moving radially outwardly alongthe lower end face of armature 33. Such a pressurization of the upperend face of armature 33 pushes the latter against the pole core 34 in anundesirable manner, because the circular relief groove 60 on the upperface of pole core 34 encloses a smaller pressure area than thatpresented by the upper end face of armature 33. A small hydraulicpressure buildup on the armature is therefore sufficient to produce ahigher pressure inside bore 59. Such an autonomous readjustment of theelectromagnetic metering valve is not desirable. In order to avoid thisphenomenon, the armature 33 is provided with a peripheral skirt 58,preferably of a magnetically non-permeable material, the skirt 58deflecting the oil stream downwardly so as to prevent any pressurebuildup in the space 62 above the armature.

A short-circuiting ring 63 in the lower end face of armature 33eliminates any humming tendency of the latter.

It should be understood, of course, that the foregoing disclosuredescribes only preferred embodiments of the invention and that it isintended to cover all changes and modifications of these examples of theinvention which fall within the scope of the appended claims.

What is claimed is:

1. In an oil burner system adapted for the continuous combustion of fueloil with air, a control device for adjusting the combustion rate of theburner comprising in combination:

a fuel oil pump connected to an oil reservoir, said pump being driven bya motor at a substantially constant speed, thereby supplying asubstantially even flow of oil to the system;

a combustion air blower being similarly driven at a substantiallyconstant speed, thereby supplying a flow of combustion air to thesystem;

a burner head including an atomizer nozzle by means of which the fueloil and combustion air are mixed and combusted;

a fuel oil supply line leading from said pump to the atomizer nozzle,including a bypass junction in said line;

a fuel oil return line leading from said bypass junction to the fuel oilreservoir;

an electromagnetic metering valve in said return line for adjustablythrottling the oil flow therein so as to determine an adjustable fueloil supply pressure and flow rate in the oil supply line;

means for adjustably pre-setting the throttling action of the meteringvalve independently of other adjustments in the system by adjusting itselectric current;

an air supply line leading from the outlet side of said blower to theatomizer nozzle; and means for adjustably throttling the air flow at theintake side of said blower so as to adjust the rate of 5 air flow inresponse to said adjustable fuel oil supply pressure in such a way thatthe rate of air flowing through the blower is increased as the oilsupply pressure increases. 2. An oil burner control device as defined inclaim 1, 10 wherein:

the electromagnetic metering valve includes a field coil and an axiallymovable armature inside the coil, the magnetic field of the coil biasingthe armature toward a flow throttling position with a force thatincreases with increasing coil current; the metering valve furtherincluding a stationary pole core which cooperates with the movablearmature to create the throttling action of the valve; and

the valve adjustment controlling means includes means for adjusting saidcoil current.

3. An oil burner control device as defined in claim 2,

wherein:

the movable armature has agenerally fiat throttling surface facing thepole core;

the pole core has a cooperating flat throttling seat facing thethrottling surface of the armature, the seat area being bounded by arelief groove whose diameter is considerably smaller than the diameterof the armature; and

the path of the fuel oil return line through the metering valve includesa central entry bore through the pole core to its throttling seat andone or more radially spaced exit channels in the pole core whichcommunicate with the relief groove.

4. An oil burner control device as defined in claim 3,

wherein:

the metering valve armature includes a peripheral skirt which surroundsits throttling surface and extends toward the pole core so as to deflectthe oil flow toward the latter and into the exit channels.

5. An oil burner control device as defined in claim 1',

further including:

a pressure check valve in the fuel oil supply line and means for biasingthe check valve toward its closed position against the fuel oil flow,the valve biasing means being so calibrated that the check valve remainsclosed, when less than a predetermined supply pressure is established inthe supply line upstream of the check valve.

6. An oil burner control device as defined in claim 5,

wherein:

the check valve is a ball-type back pressure valve arranged between thesupply line bypass point and the atomizer nozzle; and

the valve biasing means is a compression spring.

7. An oil burner control device as defined in claim 5,

wherein:

the check valve is a plunger valve which includes a moving plunger; and

the valve-biasing means is a spring which engages one end of theplunger, urging the latter into its closed position against the supplypressure in the fuel oil supply line which impinges on the plunger fromthe opposite end. 8. An oil burner control device as defined in claim 7,wherein:

the burner head includes a bypass-type atomizer nozzle to which thesupply line feeds fuel oil, the bypass junction of the supply line beingpart of said atomizer nozzle;

the plunger valve is arranged in the oil supply line between the fueloil pump and said bypass point, and further includes a pressure reliefline between it and the fuel oil reservoir;

the fuel oil supply line and the valve plunger define a first closingoverlap in the closed valve position and the pressure relief line andthe valve plunger define a second, larger closing overlap in the sameclosed valve position; and

the valve biasing means is so calibrated that the valve plungerdisplacement is less than said first closing overlap as long as the oilsupply pressure determined by the metering valve is below apredetermined value, and is more than said second closing overlap whenthe supply pressure exceeds a predetermined value.

9. An oil burner control device as defined in claim 1,

wherein:

the combustion air blower includes a blower housing and an air intakeopening defined by said housing; and

the air flow throttling means is a clappet valve at the air intakeopening, the clappet valve including a means for biasing it toward itsclosed position, and a hydraulic cylinder means for progressivelyopening it against the biasing means, as the pressure in the fuel oilsupply line increases. 10. An oil burner control device as defined inclaim 9, wherein:

the hydraulic cylinder means includes a control line connecting it tothe fuel oil supply line. 11. An oil burner control device as defined inclaim 9, wherein:

the hydraulic cylinder means includes a control line connecting it tothe fuel oil return line upstream of the throttling means in the latter.12. An oil burner control device as defined in claim 1, wherein:

the fuel oil pump is a positive displacement pump producing a constantoil flow rate independent of the counter-pressure to be overcome in thesupply line; and the combustion air blower is rotatably coupled with thefuel oil pump.

1. In an oil burner system adapted for the continuous combustion of fueloil with air, a control device for adjusting the combustion rate of theburner comprising in combination: a fuel oil pump connected to an oilreservoir, said pump being driven by a motor at a substantially constantspeed, thereby supplying a substantially even flow of oil to the system;a combustion air blower being similarly driven at a substantiallyconstant speed, thereby supplying a flow of combustion air to thesystem; a burner head including an atomizer nozzle by means of which thefuel oil and combustion air are mixed and combusted; a fuel oil supplyline leading from said pump to the atomizer nozzle, including a bypassjunction in said line; a fuel oil return line leading from said bypassjunction to the fuel oil reservoir; an electromagnetic metering valve insaid return line for adjustably throttling the oil flow therein so as todetermine an adjustable fuel oil supply pressure and flow rate in theoil supply line; means for adjustably pre-setting the throttling actionof the metering valve independently of other adjustments in the systemby adjusting its electric current; an air supply line leading from theoutlet side of said blower to the atomizer nozzle; and means foradjustably throttling the air flow at the intake side of said blower soas to adjust the rate of air flow in response to said adjustable fueloil supply pressure in such a way that the rate of air flowing throughthe blower is increased as the oil supply pressure increases.
 2. An oilburner control device as defined in claim 1, wherein: theelectromagnetic metering valve includes a field coil and an axiallymovable armature inside the coil, the magnetic field of the coil biasingthe armature toward a flow throttling position with a force thatincreases with increasing coil current; the metering valve furtherincluding a stationary pole core which cooperates with the movablearmature to create the throttling action of the valve; and the valveadjustment controlling means includes means for adjusting said coilcurrent.
 3. An oil burner control device as defined in claim 2, wherein:the movable armature has a generally flat throttling surface facing thepole core; the pole core has a cooperating flat throttling seat facingthe throttling surface of the armature, the seat area being bounded by arelief groove whose diameter is considerably smaller than the diameterof the armature; and the path of the fuel oil return line through themetering valve includes a central entry bore through the pole core toits throttling seat and one or more radially spaced exit channels in thepole core which communicate with the relief groove.
 4. An oil burnercontrol device as defined in claim 3, wherein: the metering valvearmature includes a peripheral skirt which surrounds its throttlingsurface and extends toward the pole core so as to deflect the oil flowtoward the latter and into the exit channels.
 5. An oil burner controldevice as defined in claim 1, further including: a pressure check valvein the fuel oil supply line and means for biasing the check valve towardits closed position against the fuel oil flow, the valve biasing meansbeing so calibrated that the check valve remains closed, when less thana predetermined supply pressure is established in the supply lineupstream of the check valve.
 6. An oil burner control device as definedin claim 5, wherein: the check valve is a ball-type back pressure valvearranged between the supply line bypass point and the atomizer nozzle;and the valve biasing means is a compression spring.
 7. An oil burnercontrol device as defined in claim 5, wherein: the check valve is aplunger valve which includes a moving plunger; anD the valve biasingmeans is a spring which engages one end of the plunger, urging thelatter into its closed position against the supply pressure in the fueloil supply line which impinges on the plunger from the opposite end. 8.An oil burner control device as defined in claim 7, wherein: the burnerhead includes a bypass-type atomizer nozzle to which the supply linefeeds fuel oil, the bypass junction of the supply line being part ofsaid atomizer nozzle; the plunger valve is arranged in the oil supplyline between the fuel oil pump and said bypass point, and furtherincludes a pressure relief line between it and the fuel oil reservoir;the fuel oil supply line and the valve plunger define a first closingoverlap in the closed valve position and the pressure relief line andthe valve plunger define a second, larger closing overlap in the sameclosed valve position; and the valve biasing means is so calibrated thatthe valve plunger displacement is less than said first closing overlapas long as the oil supply pressure determined by the metering valve isbelow a predetermined value, and is more than said second closingoverlap when the supply pressure exceeds a predetermined value.
 9. Anoil burner control device as defined in claim 1, wherein: the combustionair blower includes a blower housing and an air intake opening definedby said housing; and the air flow throttling means is a clappet valve atthe air intake opening, the clappet valve including a means for biasingit toward its closed position, and a hydraulic cylinder means forprogressively opening it against the biasing means, as the pressure inthe fuel oil supply line increases.
 10. An oil burner control device asdefined in claim 9, wherein: the hydraulic cylinder means includes acontrol line connecting it to the fuel oil supply line.
 11. An oilburner control device as defined in claim 9, wherein: the hydrauliccylinder means includes a control line connecting it to the fuel oilreturn line upstream of the throttling means in the latter.
 12. An oilburner control device as defined in claim 1, wherein: the fuel oil pumpis a positive displacement pump producing a constant oil flow rateindependent of the counter-pressure to be overcome in the supply line;and the combustion air blower is rotatably coupled with the fuel oilpump.